In emulsion polymerization of polymers, an emulsifier is used. For example, in a process of producing a fluoropolymer by homopolymerization or copolymerization of fluorine-containing monomers, a fluorine-containing organic acid such as a fluorocarboxylic acid is used as an emulsifier. Considering the fact that a fluorine-containing organic acid such as a fluorocarboxylic acid is generally expensive and have an effect on the environment, it is usually desirable to recover the fluorine-containing organic acid.
WO 2013/038990 (Patent Document 1) describes a method of recovering an anionic fluorine-containing emulsifier by eluting and recovering an anionic fluorine-containing emulsifier as an acid of the anionic fluorine-containing emulsifier from a base-type ion-exchange resin having adsorbed the anionic fluorine-containing emulsifier. It is described in Patent Document 1 that according to this method, the acid of the anionic fluorine-containing emulsifier used in production of fluoropolymers can be recovered with a high yield and that the acid of the recovered anionic fluorine-containing emulsifier can directly be used for emulsion polymerization of fluoropolymers.
WO 2010/113720 (Patent Document 2) describes a method of adsorbing a fluorocarboxylic acid in which a fluorocarboxylic acid is adsorbed to activated carbon by contacting a liquid containing a fluorocarboxylic acid having an ether bond with the activated carbon. It is described in patent document 2 that a fluorocarboxylic acid having an ether bond can efficiently and selectively be removed from a liquid phase such as factory wastewater, domestic wastewater, and rivers.